2665. What characters can be added here so that each character contains a part of the previous character? a) 柔 -> _ -> _ -> 腰 b) 姿 -> _ -> _ -> 含

a) 柔 -> 棋 -> 期 -> 腰  

柔  JUU, NYUU, yawa(rakai) - soft

棋  KI - go, shogi, Japanese chess

期  KI, GO - time, period, term

腰  YOU, koshi - pelvis, loins, hips, back

b) 姿 -> 如 -> 吟 -> 含  

姿  SHI, sugata - figure, form, shape, appearance

如  JO, NYO - equal, like, as, as if

吟  GIN - sing, chant, recite

含  GAN, fuku(mu), fuku(meru) - hold, include, contain